1. Field of the Invention
This invention relates to a wick for oil burning appliances, and more specifically, to a wick for oil burning appliances using liquid fuels such as kerosene, for example, kerosene stoves and kerosene space heaters, etc.
2. Description of the Prior Art
A wick for use in oil burning appliances consists of a fuel absorbing section in which a liquid fuel is absorbed by capillary action, and a burning section in which the absorbed fuel is burned to produce high temperatures. Although the fuel absorbing section and the burning section cannot be clearly distinguished from each other, the wick being used in a burning appliance may be significantly evaluated by dividing it conceptually into the fuel absorbing section and the burning section and assessing the performance of each of these sections.
A typical example of the wick which has long been used in burning appliances consists of a fuel absorbing section composed of a thick woven fabric of cotton yarns or cotton/rayon blended yarns, and upwardly thereof, a burning section composed of a flame-resistant thick woven fabric of glass fiber yarns or glass fiber/carbon fiber blended yarns, for example, PYROMEX (a trade name for a product of Toho Rayon Co., Ltd.). Conventional wicks having such a structure are described, for example, in Japanese Laid-Open patent publication No. 5229/1979 and U.S. Pat. No. 1,651,209. The former discloses a wick consisting of a burning section composed of heat-resistant fibers such as glass fibers and asbestos, and a fuel absorbing section composed of a woven fabric of hydrophobic and oleophilic synthetic fibers such as polypropylene and polyethylene fibers, the two sections being sewn together. The latter discloses a wick consisting of a lower portion of cotton and an upper portion of an asbestos woven fabric.
These conventional wicks, however, have the defect that since a special loom must be used to produce the thick woven fabric the productivity is low and the cost of production is high. Specifically, the thick woven fabric is produced by using ultrathick cotton yarns, for example 8 folded yarns of 10.sup.s, as warps. Moreover, the fabric has a special weave and a small width. For this reason, such a woven fabric cannot be produced on an ordinary loom nor with high productivity.
There has been known an attempt to produce a thick wick for burning appliances without using a special loom by a method which comprises separately providing a woven or knitted cloth composed mainly of glass fibers and a felt having a flat smooth surface and composed mainly of glass wool, laying the felt over one or both surfaces of the woven or knitted cloth, and needle-punching the assembly by a needling machine to unite them into a unitary structure (see Japanese utility model publication No. 13978/1970). According to the disclosure of this patent document, the wick has the advantage that because the fibers of the felt are entangled with the woven or knitted cloth, the fuel is prevented from flowing down along the woven or knitted cloth, and therefore, the burning can be started rapidly upon re-ignition.
Wicks of similar structures are disclosed in Japanese Laid-Open utility model publication No. 75434/1975 in which a felt obtained by entangling metallic fibers or carbon fibers and compressing the entangled mass is used instead of the felt having a flat smooth surface and composed mainly of glass wool similar wicks are also disclosed in Japanese Laid-Open utility model publication No. 140732/1974 in which a felt composed mainly of carbonized wool-like acrylic fibers having higher heat resistance than glass fibers is used instead of the aforesaid felt. Since these wicks use a woven or knitted fabric composed mainly of glass fibers, it is apparent that they have an improved oil-retaining property as in the aforesaid wick.
U.S. Pat. No. 214,085 discloses a lamp-wick consisting of one or more layers of parallel threads of fine-spun glass enclosed in a textile material, the whole being sewed together by a series of parallel longitudinal stitches. The lamp-wick of the prior art is produced by enclosing one or more layers of parallel threads of glass in a textile material and sewing the whole together. Since the glass threads are liable to spread easily, a great deal of effort is required in maintaining them parallel to each other. Furthermore, since the outermost layer of the wick is the textile material, channels tend to form longitudinally along stitches during the stitching operation. Therefore, the manufacturing process is complex and unsuitable for mass production. The longitudinal channels worsen the fit of the wick with the wick guiding slit of a burning appliance. Furthermore, as the temperature of the oil rises by burning, the gas in the oil tank goes up along these channels to flame up intermittently. There also is a danger of ready leakage of the oil in the event of overturning the burning appliance. In addition, since the textile material is stitched, the wick has the defect of shrinking when immersed in the oil.